Screen



Feb. 2 1926.

H. J. REED El AL 2 Sheets-Sheet 1 SCREEN Filed April '7, 1925 1721282220716. H0 r020? JEeeaZ,

' jlllllllllllllllltlllllll Feb; 2, 1926. 1,571,736

, H. J. REED ET AL SCREEN Filed April '7, 1925 Y 2 Sheets-Sheet 2 Patented Feb. 2, 1926.

1,57l,73ti

Ul llTEl) STATES PATENT oFFicE.

HAROLD J. REED, OF NASHUA, NEW HAMPSHIRE, AND CLAUDE L. S PAFFORD, OF HER-BROOKE, QUEBEC, CANADA, ASSIGNORS TO IMPROVED PAPER MACHINERY COT/IPANY, OF NASHUA, NEW HAMPSHIRE, A CORPORATION OF IVIAINE.

SCREEN.

Application filed April 7, 1925. Serial No. 21,285.

To all 1071 0922, it may concern:

Be it known that we, IIAROLD J. Eran, a citizen of the United States, and a resident of Nashua, in the county of Hillsborough and State of New Hampshire, and CLAUDE L. Sherman, a subject of the King of Great Britain, and a resident of Sherbrooke, in the Province of Quebec, Canada, have invented an Improvement in Screens, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings representing like parts.

This invention relates to screens and more particularly, though not exclusively, to screens intended for screening pulp in paper manufacture, such, for example, as those where the diluted st ck is fed to a screen drum, usually the interior thereof, and there acted on by devices, such, for example as impelling blades, the liner fibres being thereby passed through the meshes of the screen, while the coarser particles or tailings are discharged from the edge thereof.

The invention, which has for its object an improvement in the effectiveness and construction of such screens, will be best understood by reference to the following description when taken in connection with the accompanying illustration of one specific embodiment thereof, while its scope will be more particularly pointed out in the appended claims.

In the drawings,

Fig. 1 is a cross sectional elevation showing the principal working parts of screen embodying one foim of the invention.

Fig. 2 is a detail in cross section and on a slightly enlarged scale showing one of the deflectors;

F 3 is a fragmentary plan View on an enlarged scale showing opposite end portions of the screen (train and the method employed of uniting sections thereof by means of deflector blades;

Fig. at is a sectional elevation taken on the line l1'- in 5 and also showing the drum supporting walls of the screen casing; and

Fig. 5 is an elevation in transverse section taken on the line in Fig. 3.

Referring to the drawings, we have there shown one form of the invention as applied to a horizontal centrifugal screen of the type and construction illustrated in our co-pend within the foraminous screen drum 15,,

whence it is distributed from suitable supply orifices lengthwise the drum to be acted on by a series of blades or impellers 17, the latter rotated by the drive shaft 19 through an orbital path in proximity to the inner walls of the screen drum. The blades are so shaped and arranged that the finer stock is impelled through the line mesh of the screen, the coarser particles or tailings incapable of passing through the screen being worked alongthe interior of the drum to the opposite ends thereof where they are delivered to a suitable tailings outlet (not shown).

The finer fibres of the diluted stock are forced through the screen into the screenedstock chamber 20 which is provided by the annular space formed between the screen drum 15 and the outer casing 21.

The screened stock gravitating down to the bottom of the chamber 20, escapes through the screened-stock delivery outlet 23. This action contemplates a constant gravitating flow of diluted screened stock from the upper part of the screen drum and screened-stock chamber to the bottom of the latter, which flow rapidly increases in volume from the uppermozt part of the screen drum toward the bottom thereof each successive lower portion, of the screen plate adds its accession of screened stock to that which has passed through the perforations of the preceding upper portions.

In a screen of the general type illustrated, the screened stock forced through the top of the screen, as soon as its momentum is checked, tends to gravitate back against the screen drum flowing down at each opposite side. The weight and pressure of the mass of fibre-charged water thus bearing against the outside of the screen drum increase rapidly from the top to the sides owing to the rapid inc'rease in volume as the screened stock from each successive portion of the screen is added. The weight or density of this water mass bearing against the screen plate, however, materially reduces the effectiveness of the screen, for it increases by just so much the force acting to oppose the passage of the stock through the screen ant against which the impellers must work. As the stock flows down over the top of the screen, furthermore, the fibre suspended therein tends to settle against the outside ot the screen drum, increasing its resistance to the passage of the stock through the screen plate and also at times tending to accumulate and clog more or less the screen meshes.

It is an advantage to force the stock through the screen under a moderate pressure, since an excessive pressure not only wastes power but may result in too violent an action by the impellers on the stock.

In the disclosed embodiment ct our invention, we have provided means, herein in the form of deflecting devices, whereby the stock passing through upper portions of the screen drum is diverted in its gravitational flow away from the adjacent lower portions of the screen drum, so that the resistance of the screened stock to the passage of stock through those lower adjacent portions of the screen drum, due to unobstructed contact therewith by this diluted stock mass, is materially lessened, thereby greatly increasing the effectiveness of the scree rand permit-- ting its operation under a mlnimum expenditure of power.

Such means for deflecting or diverting the.

stock from the screen drum surface might assume various forms, all within the spirit of our invention, and such means might be secured to or formed as a part of the external casing surrounding the drum, but herein we have provided deflecting devices secured to the screen drum itself, S llCl1 '(l8- vices in part being also utilized in simplifying the construction of the drum.

Referring to the deta ls of this embodiment of the invention (Flgs. 3, l and 5), the ioraminous surface of the drum is formed in two or more segmental sections, as and 15 and at the line of separation are clamped together by clampingplatcs and 27 extending lengthwise the drum and riveted or otherwise secured longitudinally at suitable intervals to the respective drum sections 15 and 15". the plates 25 being provided with a prolonged inclined deflecting blade or wall 29 extending its entire length. r

The plate 25 overlaps the joint 31 between the drum sections 15 and 15 and has its edge abutting against and slightly overlapping the opposing edge ot-the plate 27. At suitable intervals there are formed on the plate 25 at the back of the deflecting blade 29 bosses or thickened portions 33 which register with and seat against lugs 35 formed on the plate 27.. At each lug there is provided a clamping bolt 37 and nut 39 by means of which the two plates may be clamped rigidly together, at the same time uniting the two drum sections. The plates 25 and 27 are herein shown as prolonged slightly beyond the edges of the screen drum whereby they rest in a grooved flange 41 formed in the screen casing thereby supporting the screen drum thereon. To hold the drum against movement each overlying end of the plate is provided with a dowel pin 43 adapted to fit an opening or recess in the supporting flange 4-1.

The screen drum; may be sub-divided into any desired number of sections and the sections united by devices of the type described. the deflecting blades being suit JLV located and inclined to secure the desired results. In the illustrative form of invention, for the purpose of illustration we have shown the screen drum (Fig. 1) as consisting merely of two parts, an upper and a lower section, the deflecting blades 29 being located at the sides of the drum and their shape and dimensions being such as to adapt them to their positions at those places.

At points above the deflectors 29, other deflecting blades may be employed of any desired number and location. lVe have herein shown two sets of such blades 4-5 and 4:19, differing only in shape, position and dimensions. These consist of deflecting members, such as the curved blade 45 (see Fig. 2), held in close relationship to the screen drum by means of lugs 47 which are riveted. or otherwise secured to the marginal edges of the drum, or, it required for purposes of reinforcement, they may be secured to the drum at intermediate points additional lugs 47. These blades leave substantially the entire surface of the screen available for effective screening, except the very narrow portion underlying the inner edge of the blade.

The shape, construction and dimension of the blades may be widely varied. Herein the angle and shape of each successive deflecting blade are slightly changed. The stock discharged from the top of the screen encounters the upper blade 49 which is shaped to divert the flow toward the outer casing and keep it away from the next lower portion of the drum. The stock flow from the top of the screen is there joined by the flow from said next lower portion and the egate mass passed over the deflector plate by which it is so diverted that it continues its outward flow away from the next successive portion oi the screen drum. Finally the stock flow, further augmented by the accession of stock passed through the screen portion below the deflector 45, engages the deflector plate 29 and is thereby deflected well toward the casing and out of range of interference with the screening action of any portion of the underlying drums.

In the application of this principle of diverting the flow of stock passed through an area or portion of the screen drum from the adjacent lower portion of the drum, the upper portions and sides of the screen drum, as well as the under portions thereof, are left free to perform their screening functions under conditions of maximum efficiency. The screen drum is relievezl of a substantial part of the mass and pressure of the screened stock flow, the tendency toward accumulations of fibre on the foraminous surface of the drum is reduced, the power required for operating the impellers is diminished, and it is possible to carry on the screening operation under a less violent movement of the impeller blades.

By the use of the pairs of plates employed in clamping together the segmental sections of the screen, a sufficient reinforcement of the screen may be secured in practice through the use of these plates without the necessity of employing circumferential or other stiffening members, and the screen thus formed may be fixedly held in position on the walls of the casing by the prolonged ends of the clamping plates 25. By this means a very simple but adequately strong screen may be had capable of effectively carrying out the screening operation.

While we have herein shown and described for the purpose of illustration one specific embodiment of the invention, it is to be understood that extensive deviations in form and relative arrangement of parts may be made therefrom and that the invention may be usefully applied to other types and constructions of screens, all without departing from the spirit thereof.

Claims:

1. In an apparatus of the class described, the combination with a casing, of a screen drum within the casing and providing a screened-stock chamber between the casing and the drum and a screening chamber within the drum, impelling devices within the screening chamber, and means in the screened-stock chamber to deflect away from the lower adjacent portion of the screen drum the gravitating stock passed through the upper part thereof.

2.. In an apparatus of the class described, the combination with a casing of a screen drum within the casing and providing a screened-stock chamber between the casing and the drum and a screening chamber within the drum impelling devices within the screening chamber, and means in the screenedstock chamber to deflect away from the lower adjacent portion of the screen drum the gravitating stock passed through the upper part thereof, said means comprising one or more deflecting walls arranged in cooperative relation to the exterior surface of the drum.

8. In an apparatus of the class described, the combination with a screen, of impeller means for passing the stock through the screen, and meansfor diverting the flow of the screened stock passed through a portion of the screen from an adjacent portion thereof.

4:. In an apparatus of the class described, the combination with a screen drum having a screened-stock chamber outside the same, of screenottstock, diverting means for opposing the tendency of the screened stock passed through the screen drum to gravitate against the drum.

5. In an apparatus of the class described, the combination with a screen drum, of means for passing stock through the drum, and devices. for deflecting the flow of the screened stock away from adjacent portions of the drum.

6. In an apparatus of the class described, the combination with a horizontally arranged screen drum, of impelling means within the drum, and a deflecting wall arranged above the drum to divert the screened stock passed through the upper part thereof away from adjacent lower portions of the drum.

7. In an apparatus of the class described, the combination with a screen drum, of impelling means within the drum, and a deflecting wall extending lengthwise the exterior of the drum and secured thereto to deflect the flow of screened stock away from the drum.

8. In an apparatus of the class described, the combination with a screen drum, of impelling means within the drum, and a plu- I rality of inclined deflecting walls cooperatively arranged in successive relation to adj acent portions of the drum whereby screened stock passed through one portion of the drum is diverted from the next adjacent portion.

9. In an apparatus of the class described, a screen drum formed of segmental sections, and an inclined deflecting plate secured to the edge of a section and serving also to unite it to the next adjacent section.

10. In an apparatus of the class described, a screen drum formed by segmental sections united by pairs of plates extending lengthwise the drum and secured one to the edge of each section, one of said plates having inclined deflecting walls.

11. In an apparatus of the class described, a screen drum formed of segmental sections united by plates extending lengthwise the drum and secured one to the edge of each section, one of the plates overlapping the joint between adjacent edges and also overlapping the edge of the companion plate, and means to clamp together the said p ates;

12'. In an apparatus of the class described, a screen drum comprising a screen wall formed of segmental sections united at their edges by longitudinal extending members, the latter being prolonged beyond opposite edges of the drum, and a casing on the walls of which said prolonged ends of said members aresup'ported.

13. In an apparatus of the class described,-

a screen drum comprising a screen wall formed of segmentalsections united at their edges by longitudinal extending members, the latter being prolonged beyond opposite edges ofthe drum, a casing having circumferential, flanged walls with which the prolonged ends of the members engage, and means for holding the members on said walls and thereby fixedly supporting the screen drum.

14. The method of screening stock which consists in forcing the finer fiber thereof from the interior to the exterior of a screen drum and diverting the gra vitating flow of the stock passing through the upper portions of the drum away from the adjacent lower portions thereof.

In testimony whereof. we have signed our names to this'specification.

HAROLD J. REED. CLAUDE L. SPAFFORD; 

